A conventional air filtering device “B” for protection suits is shown in FIG. 7 and generally includes a case 7 having a top hole and a bottom hole, a filtering material 8 is received in the case 7 and a fan unit 9 is located above the filtering material 8 and faces the top hole. A hose 10 has one end engaged with the top hole and the other end of the hose 10 is in communication with an interior of the protection suit. The air is sucked into the case 7 by the fan unit 9 and filtered by the filtering material 8, and then is sent to the wearer.
However, the fan unit 9 cannot provide sufficient amount air to the wearer and the fan generates a lot of noise when in operation so that the wearer is suffered by the noise. The filtering material 8 is received in the case 7 and difficult to replace and maintain.
The present invention intends to provide an air filtering device for protection suits and includes a muffler for reducing noise from the fan unit. The filtering material is located at outside of the case so that it is easily to be replaced.